This invention relates to a printing apparatus and, more particularly to a printing apparatus which reduces the power source capacity of the printing apparatus without imposing additional load on the apparatus and varying a printing speed at every scanning, and a driving method therefor.
Conventionally, a printing apparatus, in which a power-source load varies drastically due to a printhead driving load, employs a power source of higher power in consideration of its maximum load. Otherwise, as disclosed in Japanese Patent Publication No. 4-74191, to limit power source output to a lower value than its maximum output, a maximum simultaneous driving load is calculated in advance, and a printing speed is varied in accordance with the obtained maximum simultaneous driving load. This reduces the power-source output upon reception of the maximum load within the power-source output range.
However, in the former case, since the apparatus uses a power source corresponding to the maximum load, the manufacturing cost of such power source and the size of apparatus increase as the maximum load becomes higher. This is inconvenient in the designing, manufacturing and cost effectiveness of the apparatus. In the latter case, the apparatus can use a smaller power source than that of the former case, however, a maximum simultaneous driving load must be obtained for each print-scanning, and the printing speed must be varied at every print-scanning, in accordance with necessity. This requires extremely complex control.